Sheathed-element glow plug unit and system for operating a plurality of sheathed-element glow plugs

ABSTRACT

A sheathed-element glow plug unit includes an input for connecting the sheathed-element glow plug unit to a control line, via which a sheathed-element glow plug of the sheathed-element glow plug unit is able to be controlled. The sheathed-element glow plug unit has an output, via which at least one further sheathed-element glow plug unit is able to be connected to the control line.

FIELD OF THE INVENTION

The present invention relates to a sheathed-element glow plug unithaving an input for connecting the sheathed-element glow plug unit to acontrol line, via which a sheathed-element glow plug of thesheathed-element glow plug unit is able to be controlled.

Furthermore, the present invention relates to a system for operating aplurality of sheathed-element glow plugs, including a central glowcontrol device and at least two sheathed-element glow plug units havingone sheathed-element glow plug in each case.

In addition, the present invention also relates to a method foroperating a plurality of sheathed-element glow plug units, eachsheathed-element glow-plug unit having one sheathed-element glow plug,and a central glow control device is provided for controlling thesheathed-element glow plug units.

BACKGROUND INFORMATION

Conventional sheathed-element glow plug units and corresponding systemsrequire at least one electrical line for each sheathed-element glow plugfor the supply of the individual sheathed-element glow plug, so that, inparticular in the case of applications with a multitude ofsheathed-element glow plugs, considerable wiring is required to connecta central glow control device to the various sheathed-element glowplugs.

Another disadvantage of conventional devices is that the central glowcontrol device requires a large number of plug pins and correspondinglycomplex and. expensive plug connectors in order to enable a connectionto each individual sheathed-element glow plug or sheathed-element glowplug unit.

SUMMARY

Example embodiments of the present invention provide a sheathed-elementglow plug unit of the type mentioned in the introduction, and acorresponding system as well as an operating method such that therequired wiring expenditure is low yet the functionality is not reducedin comparison to conventional systems.

According to example embodiments of the present invention, asheathed-element glow plug unit of the type mentioned in theintroduction includes an output, via which at least one additionalsheathed-element glow plug unit is able to be connected to the controlline.

In contrast to conventional systems, the arrangement of thesheathed-element glow plug unit according to example embodiments of thepresent invention, having an input and an output, allows a serialconnection of a plurality of sheathed-element glow plug units and thus alower wiring outlay than, for instance, in the case of sheathed-elementglow plug units disposed about a central glow control unit in astar-shaped topology. This reduces the number of plug pins on the glowcontrol unit.

Additional features and details of example embodiments of the presentinvention result from the following description, in which an exemplaryembodiment of the present invention is explained in detail withreference to the drawing. In this context, the features mentioned may beprovided alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system according to an example embodimentof the present invention;

FIG. 2 is a block diagram of a sheathed-element glow plug unit accordingto an example embodiment of the present invention;

FIG. 3 a illustrates a position-evaluation unit according to an exampleembodiment of the present invention;

FIG. 3 b illustrates a position-evaluation unit according to an exampleembodiment of the present invention;

FIG. 4 illustrates an additional example embodiment of the presentinvention; and

FIG. 5 is a flow chart of a method according to an example embodiment ofthe present invention.

DETAILED DESCRIPTION

FIG. 1 shows a simplified block diagram of a system 100 according to anexample embodiment of the present invention, which includes a centralglow control device 110 as well as a plurality of sheathed-element glowplug units 120 a, 120 b. System 100 is used, for example, in motorvehicles having self-igniting internal combustion engines in order topreheat the combustion chambers of various cylinders of the internalcombustion engine with the aid of sheathed-element glow plugs providedin individual sheathed-element glow plug units 120 a, 120 b.

According to example embodiments of the present invention, only thefirst of the plurality of sheathed-element glow plug units 120 a, 120 bis directly connected to central glow control device 110. As can begathered from FIG. 1, additional sheathed-element glow plug units 120 b,. . . are connected in series to first sheathed-element glow plug unit120 a. This reduces the wiring expenditure in the region of central glowcontrol device 110 in system 100. Furthermore, central glow controldevice 110 requires only a single plug pin to connect a multitude ofsheathed-element glow plug units 120 a, 120 b, etc.

Since the individual sheathed-element glow plug units 120 a, 120 bassigned to adjacent cylinders of an internal combustion engine areusually situated in close proximity to each other on account of thedesign of the internal combustion engine, the ohmic power losses in theadditional sections 110 b, 110 c of control line 110, each of which, byitself, is considerably shorter than a connection line between centralglow control device 110 and a sheathed-element glow plug unit of theconventional type, are lower than in line connections of conventionalsystems.

FIG. 2 shows a block diagram of a sheathed-element glow plug 120according to an example embodiment of the present invention.Sheathed-element glow plug units 120 a, 120 b, for example, which areshown in FIG. 1, also have the same configuration.

As can be gathered from FIG. 2, sheathed-element glow plug unit 120 hasan input 10 and an output 20. Via input 10, sheathed-element glow plugunit 120 is able to be directly connected to control line 110 a, forexample, which originates from central glow control device 110, whileoutput 20 of sheathed-element glow plug unit 120 is connected to aninput 10 of an additional sheathed-element glow plug unit 120, forinstance via an additional section 110 b (FIG. 1) of control line 110 a,110 b, 110 c.

Via an electrical connection of input 10 to output 20 within firstsheathed-element glow plug unit 120 a, control line 110 a, which isconnected to input 10 of first sheathed-element glow plug unit 120 a(FIG. 1), is able to be connected through to first sheathed-element glowplug unit 120 a and can thereby be made available to followingsheathed-element glow plug units 120 b, . . . . The connection of input10 to output 20 may be implemented by, for instance, correspondingswitches, which are preferably embodied as low-impedance semiconductorswitches. In the same manner, additional sheathed-element glow plugunits 120 b, . . . are able to determine whether control line 110 b, 110c, . . . is connected through to a following sheathed-element glow plugunit, which allows a corresponding forwarding of control signals that,for example, are transmitted from central glow control device 110.

To coordinate local control processes such as the connection of an input10 to an output 20, and to implement diagnostic sequences and the like,sheathed-element glow plug unit 120 (FIG. 2) has a local control unit40, which is preferably embodied as microcontroller or asapplication-specific, integrated circuit, ASIC.

Local control unit 40 is also used to evaluate control signals whichcentral glow control device 110 outputs to sheathed-element glow plugunits 120 a, 120 b, . . . via control line 110 a, 110 b, 110 c.

To receive such control signals, sheathed-element glow plug unit 120 hasa communications unit, which, for instance, evaluates a voltage levelbetween control line 110 a, 110 b, 110 c and a reference potential, suchas the ground potential, by which corresponding address signals andcontrol signals from central glow control unit 110 are encoded. In thesame manner, i.e. by ground sampling, the communications unit ofsheathed-element glow plug unit 120 is also able to generate signals andtransmit them via control line 110 a, 110 b, 110 c.

For sheathed-element glow plug unit 120 to know its address code, itmust be able to detect its position within a series connection of aplurality of sheathed-element glow plug units 120 a, 120 b, . . . (FIG.1). To this end, it is equipped with a position-evaluation unit, whichis denoted by reference numeral 30 in the block diagram according toFIG. 2.

Position-evaluation unit 30 has at least one resistive and/or inductivecomponent, which is switchable between input 10 and output 20 during theposition detection process. This results in a voltage-divider systembetween input 10 of first sheathed-element glow plug unit 120 a and theoutput of the last sheathed-element glow plug unit, which is preferablyconnected to the ground potential during the position determination, thevoltage-divider system being made up of the series connection of theresistive and inductive elements of the individual sheathed-element glowplug units 120.

When an ohmic resistor is used as resistive element, this will thereforeresult in a simple ohmic voltage divider, and if all ohmic resistors areselected to have the same resistance value, then it is easily possibleto infer the position of the particular sheathed-element glow plug unit120 within the series connection by determining the voltage betweeninput 10 and/or output 20 and the ground potential by applying thevoltage-divider rule.

FIG. 3 a shows a position-evaluation unit 30 by way of example; it hasan ohmic resistor R, which is switchable between input 10 and output 20of sheathed-element glow plug unit 120 (FIG. 2) with the aid of switches15 a, 15 b. In the example embodiment shown, device V for a voltagemeasurement is provided as well, which measures a potential differencebetween the connection terminal of ohmic resistor R, shown on the leftin FIG. 3 a, and a ground potential. After the position detection hasbeen concluded, switches 15 a, 15 b are opened and assume the stateshown in FIG. 3 a. Switches 15 a, 15 b may advantageously be embodied assemiconductor switches, in particular as field-effect transistors.

In example embodiments of the present invention, instead of ohmicresistor R and switches 15 a, 15 b, it is also possible to provide onlya single semiconductor switch in position-evaluation unit 30. In thiscase the semiconductor switch is preferably arranged as field-effecttransistor and, by appropriate controlling at its gate electrode, forinstance, allows the simulation of ohmic resistor R additionallyprovided in the exemplary embodiment according to FIG. 3 a, by its owndrain-source resistance, which comes about between its drain electrodeand its source electrode. That is to say, in this case the field-effecttransistor simultaneously realizes the functionality of switches 15 a,15 b (FIG. 3 a) to connect input 10 to output 20, and the functionalityof the serial resistor required for the position detection. The voltagemeasurement may be implemented analogously to the exemplary embodimentshown in FIG. 3 a.

FIG. 3 b shows a position-evaluation unit 30 according to an exampleembodiment of the present invention, which includes an inductive elementL, such as a coil having a specifiable inductivity. Analogously to theabove description, this produces an inductive voltage divider within theseries connection of sheathed-element glow plug units 120 a, 120 b, . .. (FIG. 1).

When central glow control device 110 applies a jump-type control signalto control line 110, the position of the corresponding sheathed-elementglow plug unit 120 may be inferred based on the individual rise time ofthe voltage dropping across a coil L, since—depending on the position ofsheathed-element glow plug unit 120—a different resulting inductivitythat influences the rise time is active on account of the seriesconnection of the coils. The voltage across coil L may then beimplemented locally using the already described means V for a voltagemeasurement, while appropriate monitoring of the rise time is preferablycarried out by local control unit 40.

Another position-evaluation unit 30 according to an example embodimentof the present invention provides a capacitive element instead ofinductive element L, which allows a position determination analogouslyto the afore-described method, and is able to be realized even moreeasily and in a more cost-effective manner than inductive element L.

Following successful position determination, each sheathed-element glowplug unit 120 a, 120 b, . . . has appropriate information and stores it,preferably in a non-volatile memory, such as an EEPROM memory integratedin local control unit 40, for example. The control of switches 15 a, 15b (FIG. 3 a) is preferably also implemented by local control unit 40.

FIG. 4 shows a module 50, which is likewise included in sheathed-elementglow plug unit 120 and has a sheathed-element glow plug 51. As can begathered from FIG. 4, a grounded connection 51 b of sheathed-elementglow plug 51 is permanently connected to the ground potential, and anoperating-voltage connection 51 a of sheathed-element glow plug 51 isconnectable to input 10 via switch 16. For example, operating-voltageconnection 51 a of sheathed-element glow plug 51 is connected to input10 via switch 16 whenever sheathed-element glow plug 51 is to betriggered. In this case, central glow control device 110 suppliessheathed-element glow plug 51 with electrical energy via input 10 andcorresponding control lines 110 a, 110 b, . . . . I.e., instead of thecontrol signals otherwise exchanged via control lines 110 a, 110 b, . .. , central glow control device 110 must then also supply an electricaloutput of sufficient size in order to ensure an adequate energy supplyof sheathed-element glow plug 51.

Sheathed-element glow plug units that are possibly situated upstreamfrom the viewed sheathed-element glow plug unit in a series connectionmust configure their modules 50 accordingly in this case, such thattheir switch 16 connects input 10 directly to output 20, so that theelectrical energy will be conveyed to sheathed-element glow plug 51 tobe triggered.

That is to say, in the case of a sheathed-element glow plug unit whosesheathed-element glow plug 51 is not to be triggered at the presenttime, switch 16 connects input 10 to output 20.

A diagnosis of the operation of sheathed-element glow plug 51 ispossible by device V, shown in FIG. 4, for a voltage measurement. Tothis end, device V could record a voltage characteristic coming about atsheathed-element glow plug 51, for instance under the control of localcontrol unit 40; in the event of a deviation from typical voltage valuesor voltage characteristics, a diagnosis report may possibly betransmitted from affected sheathed-element glow plug unit 120 to centralglow control device 110.

This makes it possible, for instance, to realize a short-circuitdetection, which infers a short circuit in the region ofsheathed-element glow plug 51 if a voltage applied to sheathed-elementglow plug 51 is undershot during triggering of sheathed-element glowplug 51. Aging of sheathed-element glow plug 51 is also detectable, by achange in the voltage characteristic coming about in the triggering ofsheathed-element glow plug 51.

Device V for a voltage measurement shown in FIG. 4 may involve the samedevice shown in FIG. 3 a as well. In this case measuring device V may bedirectly and permanently connected to input 10 and activated either forposition detection or for diagnostic purposes in an operation ofsheathed-element glow plug 51 (FIG. 4).

Device V for a voltage measurement may also be directly integrated inlocal control unit 40, for instance in the form of at least oneanalog-to-digital converter channel of a local control unit 40 embodiedas microcontroller.

The control of an electric power supplied to sheathed-element glow plug51 may, for one, be implemented by central glow control device 110 viathe selection of the voltage applied to control line 110 a, 110 b, . . .or, on the other, is able to be coordinated locally in asheathed-element glow plug unit 120, for instance by local control unit40. In a local control, local control unit 40 is able to open and closeswitch 16 according to a specified pattern, for instance, in order tothereby enable a pulse-width-modulated triggering of sheathed-elementglow plug 51.

Instead of the configuration of module 50 illustrated in FIG. 4, for thepurpose of triggering one sheathed-element glow plug 51 it is alsopossible to connect input 10 (FIG. 2) to output 20 in allsheathed-element glow plug units 120, and to optionally connectoperating-voltage connection 51 a of corresponding sheathed-element glowplug 51 to input 10 or output 20, or disconnect it therefrom, by aswitch provided in module SO. In an especially advantageous manner, aparallel triggering of sheathed-element glow plugs 51 of a plurality ofsheathed-element glow plug units 120 is possible simultaneously sinceall sheathed-element glow plug units 120 or modules 50 are supplied withelectrical energy via respective input 10. In this case it must beensured that central glow control device 110 (FIG. 1) is able to providesufficient electrical power via control line 110 a, 110 b, 110 c, . . ., and that switches provided locally in sheathed-element glow plug units120 for the connection of input 10 to the respective output 20 areconfigured for the currents that arise.

In a very advantageous manner, sheathed-element glow plug unit 120 hasan energy-supply unit, which stores electrical energy supplied tosheathed-element glow plug unit 120 via control line 110 a, 110 b, 110c, and/or makes it available to the components of sheathed-element glowplug unit 120, in particular to local control unit 40. For this purposethe energy-supply unit may, for instance, be equipped with a voltageconverter, protective diodes or also with a local charge-coupled storein a manner known per se.

A method of an example embodiment of the present invention is describedin the following text with the aid of the flow chart shown in FIG. 5.

In step 200, central glow control device 110 (FIG. 1) first applies aspecifiable voltage to control line 110 a, and individual switches 15 a,15 b of position-evaluation units 30 of the various sheathed-elementglow plug units 120 a, 120 b, . . . are closed, so that a position isable to be evaluated.

Subsequently, in step 210, the determined position of eachsheathed-element glow plug unit 120 a, 120 b, . . . is stored locally,for example in a non-volatile memory of local control unit 40. Ifapplicable, status feedback of individual sheathed-element glow plugunits 120 to central glow control device 110 may occur, in which acorresponding item of position information of the individualsheathed-element glow plug unit 120 is advantageously transmitted aswell.

In step 220, a specific sheathed-element glow plug unit 120 b istriggered. The triggering may, for example, be implemented in such amanner that central glow control device 110 first outputs the address orposition of sheathed-element glow plug unit 120 b to be triggered,possibly together with trigger parameters such as, for example, atrigger duration or a power profile or the like, using control lines 110a, 110 b, . . . .

Following successful address or position comparison, the communicationsunit of corresponding sheathed-element glow plug unit 120 b forwards theinformation received via control line 110 a, 110 b, . . . to localcontrol unit 40 of sheathed-element glow plug unit 120 b, andsheathed-element glow plug 51 of sheathed-element glow plug unit 120 bwill then be triggered accordingly.

A special advantage of system 100 is that all sheathed-element glow plugunits 120 may have the same design and are quasi able to initializethemselves via the described position detection, so that no specialsequence or the like need to be observed when sheathed-element glow plugunits 120 are installed. Furthermore, the absolute number ofsheathed-element glow plug units 120 connected to a central glow controldevice 110 is able to be determined in an uncomplicated manner.

In addition, the series connection allows a particularly uncomplicatedand low-cost wiring with power losses that are lower than inconventional systems. In a particularly advantageous manner, firstsection 110 a of the control line may have an especially large diameter,since a reduction in the power losses in this section 110 a has aneffect on all triggering processes as a result of the series connection.

The fact that only a single plug pin must be provided on central glowcontrol device 110 in system 100 is to be considered an additionaladvantage, the plug pin being utilized to connect control line 110 a.

Furthermore, measuring device V (FIGS. 3 a, 4) integrated into thecorresponding sheathed-element glow plug unit 120 makes it possible toperform a diagnosis of each individual sheathed-element glow plug 51.

A conventional protocol suitable for single-wire transmission is able tobe used for the communication of components 110, 120 via control line110 a, 110 b, 110 c, . . . . In an advantageous manner, aninterference-resistant and self-synchronizing Manchester coding is alsoemployable for the encoding of data to be transmitted.

Furthermore, it is possible to use a low-pass frequency range for theenergy transmission via control line 110 a, 110 b, 110 c, . . . , inparticular also for the supply of sheathed-element glow plugs 51, and totransmit control signal in a band-pass frequency range so that thecontrol signals may, for instance, be separated from an equisignalprovided for energy transmission, with the aid of corresponding filtersin, e.g., a conventional manner.

In general, sheathed-element glow plug unit 120 or system 100 allows theuse of sheathed-element glow plugs configured for an operating voltageof 11 Volt as well as low-voltage sheathed-element glow plugs.

To ensure reliable communication between central glow control device 110and sheathed-element glow plug units 120 a, 120 b, it may be provided asstandard state that input 10 is connected to output 20 in eachsheathed-element glow plug unit 120, via a corresponding switch, forinstance, and that the particular communications unit is activated inorder to be able to evaluate trigger signals that may arise.

1-16. (canceled)
 17. A sheathed-element glow plug unit, comprising: aninput configured to connect the sheathed-element glow plug unit to acontrol line, via which a sheathed-element glow plug of thesheathed-element glow plug unit is controllable; and an output, viawhich at least one further sheathed-element glow plug unit isconnectable to the control line.
 18. The sheathed-element glow plug unitaccording to claim 17, further comprising a local control unit.
 19. Thesheathed-element glow plug unit according to claim 17, furthercomprising a local control unit arranged as at least one of (a) amicrocontroller and (b) an application-specific integrated circuit. 20.The sheathed-element glow plug unit according to claim 17, furthercomprising a communications unit.
 21. The sheathed-element glow plugunit according to claim 17, further comprising a position-evaluationunit including at least one of (a) a resistive, (b) an inductive, and(c) a capacitive component switchable between the input and the output.22. The sheathed-element glow plug unit according to claim 21, furthercomprising a voltage measurement device configured to determine at leastone of (i) a voltage dropping at the at least one of (a) the resistive,(b) the inductive, and (c) the capacitive component and (ii) a voltagebetween a connection of the at least one of (a) the resistive, (b) theinductive, and (c) the capacitive component and at least one of (a) areference potential and (b) a ground potential.
 23. The sheathed-elementglow plug unit according to claim 17, wherein a grounded connection ofthe sheathed-element glow plug is permanently connected with a groundpotential within the sheathed-element glow plug unit, and anoperating-voltage connection of the sheathed-element glow plug isconnectable to the input.
 24. The sheathed-element glow plug unitaccording to claim 17, further comprising a voltage measurement deviceconfigured to determine at least one of (a) a voltage applied betweenthe input and the output, (b) a voltage applied between the input and areference potential, and (c) a voltage applied between the output and areference potential.
 25. The sheathed-element glow plug unit accordingto claim 17, further comprising an energy-supply unit configured to atleast one of (a) store electrical energy supplied to thesheathed-element glow plug unit via the control line and (b) supplyelectrical energy to at least one of (a) components of thesheathed-element glow plug unit, (b) a control unit, and (c) a localcontrol unit.
 26. A system for operating a plurality of sheathed-elementglow plugs, comprising: a central glow control device; at least twosheathed-element glow plug units, each including a sheathed-element glowplug; wherein, via a control line, the central glow control device isconnected only to a first sheathed-element glow plug unit, andadditional sheathed-element glow plug units are switched in series tothe first sheathed-element glow plug unit.
 27. The system according toclaim 26, wherein control signals for an operation of thesheathed-element glow plug units and electrical energy for at least oneof (a) supply of components of the sheathed-element glow plug units and(b) supply of the sheathed-element glow plugs are transmittable via thecontrol line.
 28. The system according to claim 26, wherein at least onesheathed-element glow plug unit includes: an input configured to connectthe sheathed-element glow plug unit to the control line, via which asheathed-element glow plug of the sheathed-element glow plug unit iscontrollable; and an output, via which at least one furthersheathed-element glow plug unit is connectable to the control line. 29.A method for operating a plurality of sheathed-element glow plug units,each sheathed-element glow plug unit including a sheathed-element glowplug, a central glow control device arranged to control thesheathed-element glow plug units, comprising: acting upon, by the glowcontrol device, a first sheathed-element glow plug unit, directlyconnected to the glow control device via a control line, with acorresponding control signal; and if appropriate, forwarding the controlsignal to additional sheathed-element glow plug units connected inseries to the first sheathed-element glow plug unit.
 30. The methodaccording to claim 29, wherein the control line is connected through thefirst sheathed-element glow plug unit to additional sheathed-elementglow plug units to forward the control signal.
 31. The method accordingto claim 29, wherein each sheathed-element glow plug unit determines itsposition in the series connection of the sheathed-element glow plugunits.
 32. The method according to claim 29, wherein at least one of (a)diagnosis reports and (b) status reports from a sheathed-element glowplug unit are transmitted to the central glow control device.
 33. Themethod according to claim 29, wherein the control line is used to atleast one of (a) supply consumers with electrical energy and (b) tosupply the sheathed-element glow plugs.